This application is based on Japanese Patent Application No. 2000-379103 filed on Dec. 13, 2000 and No. 2001-001983 filed on Jan. 9, 2001, the contents of which are incorporated hereinto by reference.
1. Field of the Invention
The present invention relates to a highly-viscous-fluid applying apparatus for applying a highly viscous fluid to an object, and more particularly to a technique for controlling an amount of the fluid to be applied to the object.
2. Discussion of Related Art
JP-B2-2863475 discloses an example of a highly-viscous-fluid applying or applying apparatus in the form of an adhesive applying apparatus arranged to apply a highly viscous fluid in the form of an adhesive agent to a circuit substrate in the form of a printed-wiring board. In this adhesive applying apparatus, the adhesive agent is accommodated in a syringe, and is extruded from the syringe with a compressed air introduced into the syringe, so that a suitable amount of the adhesive agent is applied to predetermined fluid-applying spots on the printed-wiring board. The amount of delivery of the adhesive agent from the syringe can be changed by adjusting the time of introduction of the compressed air into the syringe or the pressure of the compressed air. In view of this fact, the fluid applying apparatus disclosed in the above-identified publication is arranged to operate an image-taking device to taken an image of a mass of adhesive agent applied to the printed-wiring board, obtain an amount of the applied adhesive agent, on the basis of image data representative of the image, compare the obtained amount with a reference value, and adjust the time of introduction or pressure of the compressed air. If the obtained amount of the applied adhesive agent is smaller than the reference value by more than a predetermined amount, the time of introduction or pressure of the compressed air is increased. If the amount of the applied adhesive agent is larger than the reference value by more than a predetermined amount, the time of introduction or pressure of the compressed air is reduced. Thus, the amount of the adhesive agent to be delivered from the syringe to the printed-wiring board is suitably controlled.
Since the air is compressible, however, it is difficult to accurately control the amount of delivery of the adhesive agent by adjusting the time of introduction or pressure of the compressed air. Namely, the amount of delivery of the adhesive agent from the syringe does not change accurately in proportion with an amount of change of the time of introduction or pressure of the compressed air, due to compression of the compressed air. The difficulty to control the amount of delivery of the adhesive agent from the syringe increases with a decrease in the amount of the adhesive agent left in the syringe and a consequent increase in the amount of the compressed air in the syringe.
It is therefore an object of the present invention to provide a highly-viscous-fluid applying apparatus, which permits an accurate control of the amount of delivery of the adhesive agent. This object may be achieved according to any one of the following modes of the present invention, each of which is numbered like the appended claims and depends from the other mode or modes, where appropriate, to indicate and clarify possible combinations of elements or technical features. It is to be understood that the present invention is not limited to the technical features or any combinations thereof which will be described for illustrative purpose only. It is to be further understood that a plurality of elements or features included in any one of the following modes of the invention are not necessarily provided all together, and that the invention may be embodied without some of the elements or features described with respect to the same mode.
(1) A highly-viscous-fluid applying apparatus comprising:
a fluid supply device operable to supply a highly viscous fluid;
a delivery nozzle from which the highly viscous fluid is delivered;
a pump disposed between the fluid supply device and the delivery nozzle, and operable to feed the highly viscous fluid received from the fluid supply device, to the delivery nozzle;
and a pump control device operable to control the pump, for controlling an amount of delivery of the highly viscous fluid to be delivered from the delivery nozzle.
The highly viscous fluid to be delivered from the present delivery nozzle of the highly-viscous-fluid applying apparatus may be an adhesive agent, or a solder paste or cream. The pump may be a screw pump or a gear pump.
The highly viscous fluid supplied from the fluid supply device is fed by the pump to the delivery nozzle, from which the fluid is delivered onto an object. The amount of the highly viscous fluid to be fed from the pump to the delivery nozzle is substantially proportional to the operating amount of the pump, without an influence of the compressibility of compressed air conventionally used to feed the fluid. Accordingly, the amount of the fluid to be delivered from the delivery nozzle can be accurately controlled by controlling the pump with the pump control device.
(2) A highly-viscous-fluid applying apparatus according to the above mode (1), wherein the pump is a screw pump including a pump housing having a screw chamber having a circular shape in transverse cross section, the screw pump further including a screw which is substantially fluid-tightly disposed within the pump housing such that the screw and the pump housing are rotatable relative to each other, the pump control device including a pump drive device operable to rotate the pump housing and the screw relative to each other.
With the relative rotation of the pump housing and the screw, the highly viscous fluid is fed from the screw chamber and delivered through the delivery nozzle. Since the fluid has a relatively high degree of viscosity, the relative rotation of the pump housing and the screw will cause the fluid to be fed along a helical thread of the screw. The screw is substantially fluid-tightly disposed within the screw chamber, so that the fluid is substantially prevented from flowing in the reverse direction through a gap between the screw and the inner circumferential surface of the pump housing which defines the screw chamber. Accordingly, the amount of the fluid to be fed in the forward direction from the screw chamber toward the delivery nozzle is substantially proportional to the angle of relative rotation of the pump housing and the screw. By controlling the angle of the relative rotation, therefore, the amount of delivery of the fluid from the delivery nozzle can be controlled with high accuracy. Further, the diameter of the screw pump may be easily made relatively small, so that the screw pump can be disposed relatively near the delivery nozzle.
(3) A highly-viscous-fluid applying apparatus according to the above mode (2), wherein the pump housing is stationary, while the screw is rotated within the pump housing, by the pump drive device.
(4) A highly-viscous-fluid applying apparatus according to the above mode (2), wherein the screw is stationary, while the pump housing is rotated about the screw, by the pump drive device.
(5) A highly-viscous-fluid applying apparatus according to any one of the above modes (2)-(4), wherein the delivery nozzle extends from one end of the screw pump, coaxially with the screw pump.
In the above mode (5), the highly viscous fluid is fed by the screw pump in its axial direction to the delivery nozzle, and is delivered from the delivery nozzle in the same axial direction. Since the direction of feeding of the fluid is not changed, the fluid does not suffer from a flow resistance due to the change of the feeding direction, permitting an easy, smooth movement of the fluid from the screw pump to the delivery nozzle, so that the amount of delivery of the fluid from the delivery nozzle onto the object can be controlled with high accuracy.
(6) A highly-viscous-fluid applying apparatus according to any one of the above modes (1)-(5), wherein the fluid supply device is a fluid supply device of a pressurizing type arranged to pressurize the highly viscous fluid and feed the pressurized highly viscous fluid to the pump.
The fluid supply device is preferably arranged to supply the highly viscous fluid to the pump through a supply passage such that the pump and the supply passage are filled with the fluid, without air cavities left in the pump and supply passage. Where the fluid supply device is of a non-pressurizing type, consisting solely of a container accommodating a mass of the fluid and a supply passage connecting the container and the pump, the container is required to be located at a level higher than that of the pump. Where the fluid has a relatively high degree of viscosity, the fluid supply device is preferably of the pressurizing type arranged to pressurize the highly viscous fluid so that the pressurized fluid is fed to the pump.
In the above mode (6), the fluid can be delivered from the delivery nozzle onto the object while the pump and the supply passage connected to the pump are filled with the fluid, without air cavities left in the pump and supply passage, even where the container is located below the pump, and/or where the fluid has a considerably high degree of viscosity.
(7) A highly-viscous-fluid applying apparatus according to the above mode (6), wherein the fluid supply device of the pressurizing type includes:
a container accommodating a mass of the highly viscous fluid;
a compressed-air supply device operable to introduce a compressed air into an upper air chamber in the container; and
a supply passage connecting a lower end of the container and a first end portion of the screw pump opposite to a second end portion of the screw pump from which the delivery nozzle extends.
(8) A highly-viscous-fluid applying apparatus according to any one of the above modes (2), (3) and (5)-(7), further comprising:
a screw rotating device including a rotary shaft for rotating the screw of the screw pump;
a sealing device interposed between the rotary shaft and the pump housing, to maintain fluid tightness therebetween while allowing rotation of the rotary shaft.
The supply passage provided in the above mode (7) is communicated with a portion of the pump housing which is located on one side of the sealing device provided in the above mode (8), which is nearer to the delivery nozzle. The supply passage may include an annular space defined by and between the outer circumferential surface of the rotary shaft and the inner circumferential surface of the pump housing. Alternatively, the supply passage may be formed to be open in the inner circumferential surface of the pump housing, at one end portion of the pump remote from the delivery nozzle.
In the above mode (8) wherein the seating device is interposed between the rotary shaft and the pump housing, the fluid is prevented from being moved in the reverse direction toward the screw rotating device, through a gap between the outer circumferential surface of the rotary shaft and the inner circumferential surface of the pump housing. Accordingly, the highly viscous fluid can be applied to the object, by an amount which is substantially proportional to the angle of rotation of the screw.
(9) A highly-viscous-fluid applying apparatus according to the above mode (4), wherein the fluid supply device includes a container for accommodating a mass of the highly viscous fluid, the container including a supply portion having an opening from which the highly viscous fluid is supplied, and the screw is fixed to the supply portion of the container.
(10) A highly-viscous-fluid applying apparatus according to the above mode (9), wherein the supply portion of the container consists of a cylindrical portion extending from one end a body of the container, and the screw is fixedly fitted at a proximal end thereof in a first part of the cylindrical portion, the opening being formed through a second part of the cylindrical portion which is located nearer to the body of the container than the first part.
(11) A highly-viscous-fluid applying apparatus according to the above mode (9) or (10), further comprising a machine frame, and wherein the pump housing is held by the machine frame such that the pump housing is rotatable and is not axially movable relative to the machine frame, and the container is removably mounted on the machine frame such that the screw is fitted into the pump housing when the container is mounted on the machine frame, and is removed from the pump housing when the container is removed from the machine frame.
(12) A highly-viscous-fluid applying apparatus according to any one of the above modes (9)-(11), further comprising a machine frame and a nozzle holding member mounted on the machine frame, and wherein the deliver nozzle is rotatably held by the nozzle holding member.
(13) A highly-viscous-fluid applying apparatus according to any one of the above modes (9)-(11), further comprising a machine frame, and wherein the pump housing and the delivery nozzle are rotatably held by the machine frame, and the pump housing is rotatably fitted in the delivery nozzle.
(14) A highly-viscous-fluid applying apparatus according to the above mode (12) or (13), further comprising a nozzle rotating device operable to rotate the delivery nozzle relative to the container and the machine frame.
(15) A highly-viscous-fluid applying apparatus according to any one of the above modes (1)-(14), further comprising a delivery-amount detecting device operable to detect an amount of delivery of the highly viscous fluid from the delivery nozzle onto an object, and the pump control device controls the pump such that the amount of delivery of the highly viscous fluid detected by the delivery-amount detecting device is adjusted to a desired value.
The amount of delivery of the highly viscous fluid from the delivery nozzle may be detected on the basis of an outside diameter or outer size, a surface area of an outer profile, a height dimension or a volume of a mass of the fluid applied onto the object, or a combination of those parameters. Although the delivery amount can be detected with highest accuracy on the basis of the volume of the applied fluid mass, it is possible to estimate the volume of the applied fluid mass on the basis of at least one of the outside diameter, surface area and height dimension of the fluid mass. The pump control device may be arranged to control the pump such that at least one of those detected parameters coincides with a desired value. The delivery-amount detecting device preferably uses an image-taking device, but may use a height detecting device using a laser beam or a ultrasonic wave. The image-taking device may be arranged to take a two-dimensional image of the applied fluid mass in a direction perpendicular to the working surface of the object. Alternatively, the volume of the applied fluid mass may be obtained by an image-taking system as disclosed in co-pending U.S. patent application Ser. No. 09/634,257 filed Aug. 7, 2000. This image-taking system includes a light-source device or an illuminating device and a two-dimensional image-taking device. The light-source device is arranged to emit a planar light along a straight plane, while the image-taking device is disposed such that its optical axis intersects the plane of the planar light. Two-dimensional images of the applied fluid mass are taken by the image-taking device, at different positions during movements of the light-source device and the image-taking device relative to the object. Image data representative of these two-dimensional images are processed to obtain a three-dimensional geometry of the applied fluid mass, which consists of two-dimensional profiles taken in different cross sectional planes perpendicular to the working surface. In the above mode (15), the amount of delivery of the fluid from the delivery nozzle can be automatically controlled with high accuracy, on the basis of the detected actual amount.
(16) A highly-viscous-fluid applying apparatus according to any one of the above modes (1)-(15), further comprising a gap-defining portion which is disposed so as to extend in a direction of extension of the delivery nozzle, in the vicinity of the delivery nozzle as seen in a direction perpendicular to the above-indicated direction of extension, such that a free end of the gap-defining portion is located ahead of a free end of the delivery nozzle in the direction of extension and such that the gap-defining portion is moved with the delivery nozzle in the direction of extension, for abutting contact with a working surface of an object, to maintain a predetermined gap between the free end of the gap-defining portion and the working surface.
Where, the delivery nozzle consists of a nozzle body and at least one delivery tube extending from the nozzle body, the gap-defining portion may be a pin which extends from the nozzle body in parallel with the at least one delivery tube, so that the pin comes into abutting contact its free end with the working surface of the object when the delivery nozzle is moved toward the object. Where the delivery tube has a high degree of rigidity, the gap-defining portion which is L-shaped or U-shaped may be fixed to the delivery tube. For instance, the L-shaped gap-defining portion consisting of a short arm and a long arm is fixed to the delivery tube such that the delivery tube extends through the short art of the L-shaped gap-defining portion. Alternatively, the U-shaped gap-defining portion is fixed to the delivery tube such that the delivery tube extends through the bottom of the U-shaped gap-defining portion. The gap-defining portion need not be an integral part of the delivery nozzle, but may be a separate member. The gap-defining portion may be fixed to the delivery nozzle which is removably held by a nozzle holder. Alternatively, the gap-defining portion may be fixedly disposed on a member which carries the delivery nozzle and which is moved to move the delivery nozzle in a direction perpendicular to the working surface of the object when the fluid is applied onto the object.
The highly viscous fluid is delivered onto the working surface of the object while the predetermined gap is maintained between the free end or delivery end of the delivery nozzle and the working surface. This arrangement permits a high degree of consistency in the three-dimensional configuration or geometry of the fluid mass applied to the working surface of the object.
The gap-defining portion may also function as a stop for determining the position of the delivery nozzle with respect to the working surface of the object in the direction perpendicular to the working surface. This stop prevents an abutting contact of the delivery nozzle at its delivery end with the object, protecting the delivery tube or tubes of the delivery nozzle against bending or other damage due to an impact upon the abutting contact, even where the diameter of the delivery tube or tubes is relatively small.
(17) A highly-viscous-fluid applying apparatus according to the above mode (16), further comprising a machine frame, a biasing device and a stopper device, and wherein at least the delivery nozzle and the gap-defining portion are movable relative to the machine frame in an axial direction of the delivery nozzle, and are biased by the biasing device in the axial direction from a proximal end toward a delivery end of the delivery nozzle, the gap-defining portion and the delivery nozzle being normally held under a biasing action of the biasing device, at respective positions which are determined by the stopper device.
In the above mode (17) of this invention, the delivery nozzle and the gap-defining portion may be moved a relatively short distance relative to the machine frame against a biasing force of the biasing device, even after the gap-defining portion has come into abutting contact with the working surface of the object. This arrangement permits the gas-defining portion to be brought into abutting contact with the object, with a high degree of stability, for establishing the predetermined gap between the delivery end of the delivery nozzle and the working surface of the object. In addition, the biasing device functions to reduce the impact upon the abutting contact of the gap-defining portion with the object, protecting the gap-defining portion and the object against damage due to the abutting contact.
(18) A highly-viscous-fluid applying apparatus according to the above mode (17), wherein the pump includes a pump housing, and the pump housing and the delivery nozzle are not movable relative to each other and are movable together relative to the machine frame in the axial direction of the delivery nozzle.
When the delivery nozzle is axially moved relative to the machine frame, the pump housing is moved with the delivery nozzle relative to the machine frame, so that the pump housing is held in an operating state in which the highly viscous fluid is fed from the pump housing to the delivery nozzle.
(19) A highly-viscous-fluid applying apparatus according to any one of the above modes (1)-(18), further comprising a temperature control device operable to control a temperature of a mass of the highly viscous fluid, at least at a portion of the mass which is moved through the delivery nozzle for delivery thereof onto an object.
In the above mode (19), the temperature of the highly viscous fluid can be controlled to a level suitable for delivery onto the object, making it possible to control the viscosity of the fluid suitable for delivery onto the object, so that the amount of delivery of the fluid onto the object can be controlled with high accuracy.
(20) A highly-viscous-fluid applying apparatus according to the above mode (19), wherein the pump includes a pump housing and a screw disposed within the pump housing such that the screw and the pump housing are rotatable relative to each other, and the temperature control device has:
a gas passage through which a gas is circulated for heat transfer between the gap and a portion of the pump housing which surrounds the screw; and
a gas-temperature control device operable to control a temperature of the gas is circulated through the gas passage.
The gas passage may be formed such that the gas is circulated for direct contact with the portion of the pump housing surrounding the screw, or for indirect contact with that portion via other member or members. Where the gas passage is formed for indirect contact of the gas with the above-indicated portion of the pump housing, it is desirable to arrange the relevant portion of the apparatus such that the heat transfer is effected between the gas and the above-indicated portion, through thermal conduction therebetween.
The gas-temperature control device includes a heating device and a cooling device for heating and cooling the gas, for example. The temperature of the gas may be controlled to be equal to a desired temperature of the highly viscous fluid, or to be higher or lower than this desired temperature.
The highly viscous fluid is heated or cooled by the gas circulated through the gas passage, so that the temperature of the fluid is controlled to a level suitable for delivery onto the object.
(21) A highly-viscous-fluid applying apparatus according to any one of the above modes (1)-(20), wherein the delivery nozzle has a plurality of delivery tubes parallel to each other.
In the above mode (21), two or more masses of the highly viscous fluid are concurrently applied through the respective delivery tubes to respective fluid-applying spots on the object, when the screw is rotated relative to the pump housing, when the delivery nozzle is located at each coating position.
(22) A highly-viscous-fluid applying apparatus according to the above mode (21), further comprising a nozzle rotating device operable to rotate the delivery nozzle about an axis thereof which is parallel to the plurality of delivery tubes.
In the above mode (22) wherein the nozzle is rotated about its axis, the fluid-applying spots on the object which correspond to each coating position of the delivery nozzle can be moved about the axis of the delivery nozzle.
(23) A highly-viscous-fluid applying apparatus according to the above mode (22), further comprising a controller operable to control the nozzle rotating device according to a predetermined control program.
(24) A highly-viscous-fluid applying apparatus according to any one of the above modes (1)-(23), further comprising a support member, and a relative-movement device operable to move the support member and an object relative to each other in a direction parallel to a working surface of the object on which the highly viscous fluid is delivered from the delivery nozzle, and in a direction perpendicular to the working surface.
(25) A highly-viscous-fluid applying apparatus according to claim 1, wherein the fluid supply device is a fluid supply device of a pressurizing type arranged to pressurize the highly viscous fluid and feed the pressurized highly viscous fluid to the pump, the apparatus further comprising a synchronous controller operable to operate the fluid supply device of the pressurizing type, in synchronization with an operation of the pump under the control of the pump control device.
(26) A highly-viscous-fluid applying apparatus according to any one of the above modes (1)-(25), wherein the pump control device includes a reverse-operating portion operable to operate the pump by a predetermined amount in a reverse direction opposite to a forward direction after termination of an operation of the pump in the forward direction to feed the highly viscous fluid to the delivery nozzle.